Upgrade to AWS SDK v3

[misterjoshua]

Per #763, the NodeJS 14 runtime is unsupported and CDK Intrinsic Validator deployments failed, so we changed the construct to always use the latest NodeJS runtime. However, the lambda assets vended with the CDK Intrinsic Validator depend on AWS SDK v2. As of NodeJS Lambda Runtimes 18.x and later AWS SDK v3 is required.

As a short-term solution, I've bundled the AWS SDK v2 with the Lambda asset. However, this means we're now responsible for updating the AWS SDK version, which isn't desirable over the longer-term. We should upgrade to AWS SDK v3 and go back to using the runtime-provided SDK.

Due to my current project schedule, I'll have to wait a few weeks before I can make this change, unless someone else wants to take a crack at it in the meantime.